I bought some used lightning headers with O2 sensor bungs. I am putting them on a carbed engine and want to plug the sensors. A 3/8 pipe plug is just a shade to small. A 3/4 bolt almost starts in the hole, but it is obvious the threads are too coarse. Does anyone know if they are metric? Anyone know if a 18mm bolt would fit? I would hate to have to buy two 02 sensors just to plug the holes. Any help would be appreciated.

They're probably that weird ~3/8" BPT or some crap my fittings guy at the local hose joint tells me about. Same size weird fitting as on the intake manifold sensor hole etc. It's a tapered thread so nothing can get out past it when it's in properly. It needs that type of thread or it get's ruined. They make specific plugs for it. I've got Stainless ones in my intake that are solid plugs. Take a header with you to a hose shop, they'll know what size it is (you'd hope!)

Good luck!

I am hoping someone has been down this road before. I am in a small town in Wisconsin, so there are not a lot of helpful shops. I have already mounted the headers thinking getting a plug would be no big deal but that isn't the case. Taking the header off and carrying it around is a pain but I may have to go that route if I can't come up with something else.

I think I have a couple. Email me your address and I'll send you one. Its metric, I think 18 or 19 MM.

Happy Easter!!

Kirk

Its 18MM X 1.5 I just hobbled out to my garage and unfortunately I gave them away. I got them from McMaster Carr. Sorry about that.

Kirk

Just use 18x1.5 drain plugs and copper washers that most any auto parts store will have.

Thanks for the help. I knew this board would have the answer. I like the drain plug with the copper washer. Thanks.

Yup... been there... done that.

Chris

Summit Racing has them.

Just went to Advance Auto Parts and got two 18MMx1.5 drain plugs and they fit Perfect. Thanks again guys.